Centrifugal powder clutches



July 21, 1959 A. TERRY ill CENTRIFUGAL POWDER CLUTCHES Filed Feb. 1, 1956 IN V EN TOR. Jpn/02 rfperzzz BY United States Patent G CENTRIFUGAL POWDER CLUTCHES Arthur Terry III, Newtown, Conn.

Application February 1, 1956; Serial No. 562,808

2 Claims. (Cl. 192- 58) This invention relates to centrifugal powder clutches and couplings in which a rotating housing errasingand a rotor are caused to contact each other through the medium of a fine powder, so that rotation of one of these elements causes rotation of the other through the medium of the powder.

Clutches of this type have been devised heretofore and operate very successfully, except for a few minor disadvantages. One of these disadvantages is that the clutch has a tendency to produce a certain amount of drag when it is operating at low speeds, or idling. This is disadvantageous if one is using this clutch on a device where any torque is undesirable at such low or idling speed, such as a lawn mower.

Another disadvantage of the usual type of powder clutch is that if it must idle for long periods, even when torque is not objectionable, the larger sizes overheat.

Powder clutches heretofore have been completely dependent on centrifugal force for the amount of torque they can transmit. It is often desirable to engage or disengage without regard to speed, or to have some variation to the capacity always being proportional to the square of the speed. For complete control, electromagnetism, mounted so as to counteract centrifugal force and/ or to draw the powder away from either the housing or the blade by being mounted near the axis and mounted respectively in the blade or the housing, can be used.

It is therefore an object of this invention to overcome the above disadvantages and to provide a complete disengagement between the rotor and the housing, so that one will not cause a drag or motion of the other at idling and other various slow speeds.

In summary, this invention accomplishes these objects by providing small magnets, mounted preferably in the housing, to cluster or concentrate fine particles of powder in such a way as to counteract the efiect of centrifugal force, at low speeds, and at least partially to remove the powder from the area of the rotor so that there is no effective torque transmitted between the rotor and the housing through the particles at idling speeds.

These magnets can be so adjusted that their effect on the powder will begin to be overcome by centrifugal force when a specific speed is reached and at full operating speed of the unit the effect of the magnets will become negligible.

Reference is now made to the drawings, in 'which there is shown a preferred embodiment of this invention.

Fig. 1 is an elevation of the external housing of the powder clutch.

Fig. 2 is a sectional elevation through section 2-2 of Fig. 1.

Figs. 3, 4 and 5 show the stepwise evolution of the progress of the powder during start-up of a clutch.

Fig. 6 is a clutch with adjustable magnets.

Fig. 7 is a clutch with electromagnetic control of the rotor.

More particularly in the drawings, the clutch comprises housing 11 formed from two hemispheres or half sections 2,895,579 Patented July 21, 1959 bolted together with boltsl2. In operation the housing 11 is connected to first shaft 13 and rotor blade 15 is connected through bolts 22 and hub 21 to the second shaft 14. Either one of these shafts can be the driven shaft and'the alternative one the driving shaft. Iii practice the unit is partially filled with a finely-divided iron powder which alternately jams and unjams in an organized way between the rotor and the housing when the unit is operating, due to the undulations in the peripheral portion of the blade 15. A felt-sealing strip 17 prevents the escape of the powder from the unit. Ribs 11a are provided to promote the dissipation of heat from the device when in operation:

Figs. 3, 4 and 5 show the sequence of events that occur when using the device that is specifically this invention. This invention proposes to provide permanent magnets 16 and 16a shown in these fig'ures as mounted in the housing. As can be seen in Fig. 3 the fine powder 19 tends to cluster about the magnets. When the unit is not operating or when it is operating at a slow speed, such as idling speed, there is pratically no powder contacting the rotor 15 and thus there is no contact between the housing and the rotor through the powder. This means that at idling speeds there is no drag from one part of the clutch to the other part.

In Fig. 4 the next stage in the phase of the beginning of the operation of the unit is shown. As the speed increases the centrifugal force exerted on the particles begins to exceed the force exerted by the permanent magnets 16 and 16a and some of the particles are thrown to the periphery of the housing. The contact between the rotor and the housing is made in a small way through the powder at the periphery and torque is transmitted from one to the other.

Fig. 5 shows the final evolution, in which the unit is operating at its normal operating speed. Centrifugal force has overcome the effect of the magnets and the powder has positioned itself in the normal manner, with the elfect of the magnets being almost completely nullified.

In Fig. 6 there is shown a unit in which the strength of the permanent magnets is adjustable. The housing 11 has drilled therein circumferentially positioned holes 20 and 20a in which is located a magnetic bolt 21. By varying the number of such bolts evenly spaced around each side of the housing, and by threading each of these bolts farther into the housing, the eflective magnetic force may be increased, or it may be decreased by threading the bolt out from the housing. The bolt may then be locked in position by suitable means for locking this type of bolt, as is well known in the art. By varying the magnetic strength one is able to vary the point in the speed of the unit at which it will begin to drag or operate as a clutch and not be completely disengaged.

Fig. 7 shows a unit in which the magnetic force is built up in the rotor 15. In the embodiment shown in this figure an electromagnetic force is applied through the coil 24 connected by wire leads 23 to a source of electricity. The coil 24 generates a magnetic field about rotor 15 and causes the powder to be attracted to the rotor and away from the housing. When in this condition the unit is speeded up, a similar efiect will occur as was shown stepwise in Figs. 3, 4 and 5 in the embodiment shown in Fig. 7. The strength of the magnetic field can, of course, be varied by varying the electrical force applied to the coil 24 and in this way fine adjustments can be made.

I claim:

1. A centrifugal powder clutch of the sort employing a subdivided magnetizable solid material as a fluid coupling medium comprising a hollow rotatable casing adapted to be mounted on a drive shaft, the casing defin- 3 V i ing a cavity serving to contain a quantity of medium and to enclose a rotor, a rotor within said casing and coaxial therewith, said rotor and easing being relatively turnable, a finely divided medium in the cavity in an amount insuflicient to completely fill the cavity and adapted, by centrifugal action, to be disposed by rotation of the casing packingly in the peripheral portions of the cavity when the casing is rotated at high speed about its axis to thereby lockingly engage the casing and the rotor, the rotor having in its peripheral portions a plurality of radial corrugations circumferentially disposed as protrusions increasing in depth toward the periphery of the rotor, and a plurality of removable and externally adjustable magnetic screws mounted in the casing and extending inwardly to its inner wall, said screws being mounted in a portion of the casing radially outward of the axis of rotation of the casing and radially inwardly of the portions of the rotor having the radial corrugations, for attracting the magnetizable particles of the medium and for balancing the magnetic force against the centrifugal force so that at low rotational speeds the magnetic force exerts on the medium a'force slightly in excess ofthe centrifugal force on the medium at those low speeds.

2. A clutch according to claim 1, wherein said plurality of screws are disposed axially in the housing.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Dodge Bulletin, June 1955, pages 4 and 5. Div. 24.)

(On file 

